KVM: improve comment on rcu use in irqfd_deassign

The RCU use in kvm_irqfd_deassign is tricky: we have rcu_assign_pointer
but no synchronize_rcu: synchronize_rcu is done by kvm_irq_routing_update
which we share a spinlock with.

Fix up a comment in an attempt to make this clearer.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 2ca4535f4fb7..3656849f78a0 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -313,8 +313,9 @@ kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi)
                 if (irqfd->eventfd == eventfd && irqfd->gsi == gsi) {
                         /*
                          * This rcu_assign_pointer is needed for when
-                         * another thread calls kvm_irqfd_update before
-                         * we flush workqueue below.
+                         * another thread calls kvm_irq_routing_update before
+                         * we flush workqueue below (we synchronize with
+                         * kvm_irq_routing_update using irqfds.lock).
                          * It is paired with synchronize_rcu done by caller
                          * of that function.
                          */